Apparatus for sensor failure detection and correction in a gas turbine engine control system

Abstract

An improved gas turbine engine control system maintains a selected level of engine performance despite the failure or abnormal operation of one or more engine parameter sensors. The control system employs a continuously updated engine model which simulates engine performance and generates signals representing real time estimates of the engine parameter sensor signals. The estimate signals are transmitted to a control computational unit which utilizes them in lieu of the actual engine parameter sensor signals to control the operation of the engine. The estimate signals are also compared with the corresponding actual engine parameter sensor signals and the resulting difference signals are utilized to update the engine model. If a particular difference signal exceeds specific tolerance limits, the difference signal is inhibited from updating the model and a sensor failure indication is provided to the engine operator.

What is claimed is: 
     
       1. An improved gas turbine engine control system including: sensor means for sensing actual engine performance parameters and actual engine controlled parameters, control computational means for generating control signals, actuator means for receiving said control signals and for modifying the controlled parameters in order to maintain a selected level of engine performance wherein the improvement comprises: failure indication and corrective action means disposed between said sensor means and said control computational means for receiving signals from said sensor means, for receiving said control signals, and for generating signals representing real time estimates of said actual engine performance parameters and of said actual engine controlled parameters while said engine is in operation, said estimate signals being transmitted to said engine control computational means in lieu of said actual engine performance and actual controlled parameter sensor signals.   
     
     
       2. The control system of claim 1 wherein said failure indication and corrective action means operates as follows: performing a simulation of the performance of the gas turbine engine as an engine model including the interrelationships between the engine performance parameters and the engine controlled parameters and generating said estimate signals;   performing a first comparison by comparing said actual sensor signals with said estimate signals and generating difference signals corresponding to the differences between said compared signals;   updating said model in response to said difference signals; and   performing a second comparison by comparing each of said difference signals with tolerance limits and inhibiting said updating from modifying said model in response to difference signals which exceed said tolerance limits.   
     
     
       3. The control system of claim 2 wherein the magnitude of the change to said engine model produced by each difference signal is proportional to the degree of control that the engine parameter corresponding to the difference signal has over said engine model as compared with the degree of control that remaining engine parameters have over said engine model. 
     
     
       4. The control system of claim 3 wherein said tolerance limits are predetermined fixed values. 
     
     
       5. The control system of claim 3 wherein said tolerance limits are calculated. 
     
     
       6. The control system of claim 4 or 5 wherein said second comparison also provides an indication to an engine operator when any of said difference signals exceeds said tolerance limits. 
     
     
       7. The control system of claim 6 wherein said failure detection and corrective action means is comprised of a programmed digital computer. 
     
     
       8. The control system of claim 1 in which at least one of said estimate signals is representative of fuel flow to said engine. 
     
     
       9. The control system of claim 1 in which said engine includes a high pressure rotor and at least one of said estimate signals is representative of the rotational velocity thereof. 
     
     
       10. The control system of claim 1 in which said engine includes a low pressure rotor and at least one of said estimate signals is representative of the rotational velocity thereof. 
     
     
       11. The control system of claim 1 in which said engine includes a compressor and at least one of said estimate signals is representative of the pressure therein. 
     
     
       12. The control system of claim 1 in which at least one of said estimate signals is representative of the temperature of at least one point of said engine. 
     
     
       13. The control system of claim 1 in which said engine includes at least one component therein comprising variable geometry means and wherein at least one of said estimate signals is representative of the position of said variable geometry means. 
     
     
       14. The control system of claim 1 in which said engine includes a fan and wherein at least one of said estimate signals is representative of discharge pressure of said fan.